An energy efficiency case study
Each situation is case specific but in the following energy optimisation example, cleanroom experts began by taking note of the most important factors. For a pharmaceutical facility in which production is taking place under GMP conditions, the task was to set up cleanrooms of various classes (A/B, B, C, D) in an area of over 1,500 m2 while ensuring that there would be no cross-contamination, and also satisfying high cooling load requirements.
The external engineers worked closely with the future user to develop a range of concepts. During this process, the focus was on process-optimised planning that incorporated profitability analysis, with particular attention being paid to the ventilation and air-conditioning technology.
In the end, it was decided that it would be best to ventilate the cleanrooms using individual recirculation units with integrated heating and cooling registers. The intention was to install these in the intermediate ceiling area and equip them with terminal High Efficiency Particulate Air (HEPA) filtration systems. The individual recirculation units were to be fed proportionally with pre-treated fresh air.
The plan also included an air-conditioning concept that incorporated heat recovery in the central ventilation unit while allowing for “free cooling”. In other words, at certain times of the year, the cold outside is utilised for cooling the air. As a result, the cooling units can be turned off for a number of months each year – all that is required is to ensure that the necessary pumping operations continue.
The concept that was implemented also made it possible to reduce the size of the central air conditioning unit by approx. 70% in comparison with a system in which the cleanrooms are ventilated and aerated directly. The use of individual heating and cooling units for each cleanroom makes it possible to regulate usage to suit requirements – and therefore helps optimise the energy use of the entire system. Due to finely-tuned control of the pressure differentials between ‘clean’ and ‘unclean’ aeas, cross-contamination is precluded right from the start and it could only occur as a result of gross negligence.
Energy savings, such as those described here, can generally be achieved in all industries where production is carried out in cleanrooms. After all, the overall cleanroom system can be viewed as a single unit – with numerous possibilities for fine tuning at various locations and points in the process. Regardless of the potential savings that can be achieved through ventilation and air conditioning technology, however, the size and class of the cleanroom are the primary determinants of the energy consumption. Because of this, process-optimised planning is necessary right from the start.
Johann Mößlacher, Professional Engineer at Dittel Engineering, Ried, explains: “Here, optimisation involves a process of carefully determining where the limits lie. In cleanrooms in particular, this entails such things as reducing the air exchange rates, lowering the pressure differentials between individual zones, and defining processes for a lower cleanroom class. This can quickly give rise to a fear that certain standards, regulations and the threshold values mandated therein are being violated, and this often results in a tendency to over-engineer systems and facilities to be certain that all requirements are satisfied.
“Yet it is an engineer's job to question these very assumptions, so that they can design systems that comply with all necessary threshold values without exceeding them needlessly. That is the correct approach for optimising the energy consumption.”
Retroactively modifying existing cleanroom systems can also be a successful approach – as in ointment production, for example: a recirculation unit for low-turbulence displacement flow makes it possible to lower energy consumption by 32% by reducing the air flow speed from 0.45 to 0.20 m/s during times when production is not taking place. The one-off costs of €11,000 for tests and qualification can lead to annual cost reductions of €6,000 – meaning the move pays for itself within two years.
It all comes down to making good use of the leeway that is almost always available. This entails continuously comparing target and actual figures and taking new technological possibilities into account. And it is critical to remember that conventional energy meters are not enough. To properly record the relevant data in cleanrooms, specialised cleanroom expertise is a must, for when this is done, it is possible to achieve savings of 10%—20% with existing systems and, in comparison with conventional ‘off the shelf’ designs, as much as 50% for a brand new design that is precisely tailored to requirements.
The industry will be offering a clear demonstration of the fact that energy efficiency and high quality standards in cleanrooms do not have to be mutually exclusive at the Cleanzone trade fair on 17–18 October in Frankfurt am Main. For example, the “Measurement Technology: Equipment and Project Validation/Qualification” module of the Cleanzone Congress will focus on state-of-the-art measurement processes. Visitors to the Cleanzone trade fair this October will be able to return to their own operations with concrete energy reduction concepts and examples from actual practice.
More information is available online at: www.cleanzone.messefrankfurt.com
